Combination fuse cutout and switch



Dec. 15, 1953 W. D. KYLE, JR

COMBINATION FUSE CUTOUT AND SWITCH Filed April 25, 1951 IN V EN TOR.

Patented Dec. 15, 1953 UNITED STATES PATENT OFFICE Appl a io pr l 25, 1 1 Se ia Na, 22.2.89

3 Claims.

My invention relates to protective devices designed to protect electrical apparatus, such as distribution transformers, against damage by high voltage surges and other abnormal conditions in an electric circuit.

Various forms of fuse cutouts are used in power distribution systems. It frequently is to the advantage of the power companies to have circuit reclosing means for closing the circuit as quickly as possible after a fuse has ruptured in order to temporarily restore service along the line until the fuse has been replaced.

I make use of a dual characteristic fuse which is constructed in such a manner that it will react to a predetermined rise in the temperature of the transformer oil produced by low over-loads of long continuing duration and will also react to sudden surges oi current of abnormally high voltage of relatively short duration to raise the temperature of the transformer oil appreciably. In this way damage to the transformer insulation is prevented when over-loads of long duration or short circuits occur in a service line.

One object of my invention is to provide a combination dual characteristic fuse and circuit recloser mounted in a primary transformer bushing, the ohcuit being reclcsable only after excess current has ruptured the fuse.

Another object is to provide a dual characteristic fuse and circuit recloser mounted in a primary transformer bushing whereby the fuse will alternatively interrupt a circuit on a low steady overload after predetermined conditions in an electrical apparatus have occurred or on a sudden surge or short circuit condition immediately upon occurrence thereof.

It is also an object to provide a combined dual characteristic fuse and recloser wherein upon interruption of the circuit, the circuit can be easily closed manually through the recloser only after interruption.

A further object is to provide a combined fuse and switch whereby the circuit is closed through the fuse by linear motion and through the switch by rotary motion only after rupture of the fuse.

A still further object is to provide a two element transformer fuse link that is a circuit maker and breaker and includes a switch operable only after rupture of the link. i i d An object also is to provide a circuit maker and breaker mounted in a primary transformer bushing which is fusible in its first part when the temperature of the oil or other cooling agent in which it is immersed reaches a value indicating sustained overload and is rusible the sec- 2 0nd part by a load which is of insuificient duration to raise the temperature of the cooling agent in which it is immersed to a value that would fuse the first part but will damage the transformer insulation.

Specifically, it is an object to provide a bayonet type combination fuse and recloser for transformer bushings, the fuse having dual character. istics operable under either oftwo abnormal circuit conditions and the recloser being manually operable to reclose the circuit upon rupture of the fuse under either of the abnormal circuit conditions.

Other purposes will appear from time to time in the course of the specification and claims.

In the drawings which accompany this specification I have illustrated an embodiment of my invention, but I wish it to be understood that I do not in the appended claims limit the terms to such embodiment, but do embrace all embodiments which come generically within the pur- View of my inventive concept.

Figs. 1 and 2 of the disclosure of the present application are respectively substantially identical to Figs. 4 and 2 of the co-pending application of Roald H. Amundsen, Serial No. 226,077, filed May 12, 1951, and assigned to the same assicnee of the present application and in which latter application the structures are presented in various forms and in greater detail and the disclosures are claimed specifically.

Referring to the drawings:

Fig. l is a fragmentary sectional view in side elevation taken longitudinally of the axis of an embodiment of this invention.

Fig. 2 is a diagrammatic illustration of an electrical transformer embodying my invention.

Fig. 3 is a view in elevation, partly in section, showing an embodiment of my invention incorporated in a transformer which is illustrated more or less symbolically.

Like parts are designated by the same reference characters throughout the several views.

The distribution transformer- I, illustrated diagrammatically in Fig. 2, includes a primary winding I, a secondary winding 2 and a core 3.

The secondary windings 2 are connected to service lines 5 which terminate at secondary bushings 6 and are grounded at 1.

A combined fuse and switch embodying my inention is shown diagrammatically in a primary bushing at 8 with an over-load protective fuse 9 in series with and located between it and the winding I. An excess voltage device or expulsion gap H1 is placed between tho primary leads H 3 and the casing 4. A tank discharge gap is shown at I2.

Referring to Fig. l, the primary bushing 8 and the embodiment of my novel combination, I show a fiat topped cover or closure it because I believe it to be a safer form than the bayonet type top. However, it is to be understood that a bayonet type top could be substituted without deviating from my invention.

The bushing 8 is provided with skirts it in its upper part and a tubular Bakelite sleeve 32 at its lower end. enlarged ends of the bushing 8 and sleeve 32 and is spun over at its ends to hold the bushing and extension together.

The transformer bushing or housing 8 is mounted in an opening it of the casing or container s. A sealing means 30 is used to make this connection airtight. At the upper end of the porcelain bushing 8 is a terminal or ferrule ill. A cement 3! is injected between the ferrule I? and the bushing 8 to securely fasten them together. The ferrule H has an opening is in its center portion substantially co-axial with the bore in the bushing 8. On the under-side of the ferrule ll adjacent its opening it is attached a plurality of contact fingers l9 extending downwardly and inwardly so as to contact a metal projection 25 which extends downwardly from the closure 13. A gasket 2! provides a seal between the ferrule l? and closure i3. Integral with the closure i3 is a handle or operating eye 22 which is used to rotate the closure 13 by means of a stick (not shown).

A socketed line terminal clamp 23 is located at some convenient place on the ferrule H from where the electric current is conducted through the contact fingers it to the metal projection 25 to which is attached the conducor rod 26.

At the lower end of the conductor rod 26 is a threaded portion 25 which is connected with the dual characteristic fuse and switch hereafter described. This combination fuse and switch is surrounded along its length by a fibre fuse tube 28.

A metal socket 29 is encased within the upper section of the fibre fuse tube 26 and fastened to the tube 25 by means of a key 53 and in direct contact with the conductor rod 214. Extending into a bore of the metal socket 29 is a flexible link at of the dual characteristic fuse, joined to it at M by means of a low melting solder joint which is responsive to the temperature of the cooling medium in the transformer casing. A spring #12 surrounds the flexible link ti? and maintains tension thereby in the link as long as the link ii! remains joined at M. The lower ends of the link 45 and the spring 42 are anchored to a spacer 38. This spacer $3 is of sufficient diameter to loosely fill the bore within the fibre fuse tube 26. Vertical extensions in both directions of this spacer 28 serve as a means for securing the flexible fuse links 40 and 43 and their respective springs.

The second flexible link 43 of the dual characteristic fuse is held in tension by a surrounding spring 44. In reverse similar manner the link 43 is attached within a bore in a metal piece 45, joined by a solder joint At. Below metal piece ie is a resistor element 4'! which becomes warm if a sudden surge of electricity travels A sleeve 33 fits over adjacent through the circuit which may be of insufficient duration to warm the transformer oil but of sufiiient voltage to damage the transformer windings. The warmth in this resistor 41 is con:

veyed to the solder joint 46. and. dissolves the joint when it reaches some predetermined temperature thus allowing the spring 4 to recoil carrying the second flexible link 43 with it which causes the current to be broken.

Attached to the lower end of the resistor t: is a metal conductor piece 54. The lower end of the fibre fuse tube 26 is pinned to it by a key means 53. Below the metal piece 513 is a guide flange conductor member 55 and below the guide flange is a terminal rod 51. Between the guide flange 55 and the lower enclosure of the Bakelite sleeve 32 is a spring means 55 surrounding the terminal rod 51. A lead 59 connects with the terminal rod 51 thus forming the second end of the conductor.

In contact with the lead 59 is the auxiliary connection 65 which connects with the contact member 25. After the fuse has blown at either ll or -35, the circuit can be closed by rotating the handle 22 which switches the position of the conductor strap 21 so as to contact the contact piece 28.

Adjacent the spacer 48 is an opening $9 in the fibre fuse tube 25, of sufficient diameter to hold a detent 50 with its surrounding spring 55. The head of the detent 59 is held tightly against the spacer 58 by the spring 51. The detent will remain in this position until either of the fuse links breaks the circuit. The detent is then free to move into the core of the fibre fuse tube 2'6. A slot 52 in the Bakelite sleeve 32 controls the position of the circuit maker and breaker. The handle 22 cannot be rotated while the detent 59 is in the slot 52.

The use and operation of my invention are as follows:

In order to protect electrical transformers against destruction by excess current and to afford renewal of electrical service after circuit interruption, I evolved the idea of this invention. I mount a circuit maker and breaker in the primary bushing of an electrical transformer. This circuit maker and breaker includes a dual characteristic fuse link that will blow in one part as a result of low steady over-load and will blow in its second part as a result of sudden surges on the line.

A steady over-load on the service lines will gradually warm the transformer oil or other cooling medium and this heat, when a given temperature is reached, will in turn cause the solder joint M to melt and release the springs 42 and t l which will then produce a gap of sufficient length to extinguish the arc and open the circuit. If a sudden surge of current occurs and its duration is not great enough to raise the temperature of the transformer oil but may be of suflicient intensity to damage the transformer insulator, it will heat the resistor 51 and the heat in the resistor 47 will be transmitted to the solder joint '46 and dissolve the joint and thus release the springs 42 and it and produce a gap designed to extinguish the arc and open the circuit. When either of the joints 4| or 45 is destroyed the spacer 48 will be moved to one side or the other of the detent 56 and the spring 5| will move the detent radially into the space occupied by the spacer 48 and withdraw from the slot 52.

After the circuit has been opened in the manner indicated, the circuit may again be closed by rotating the bayonet through the medium of the eye 22 on the closure I3 until the conductor strap contacts the contact piece 28 and closes the circuit therethrough. It will be understood that a circuit is reestablished in the manner indicated to continue the service until the bayonet can be substituted by one in which the fuse elements are intact.

I claim:

1. A circuit interrupter and recloser comprising in combination an insulating support including relatively spaced first and second terminals, a manually operable circuit cioser movably supported by said support for movement successively between open circuit position to a normal circuit closing position, and from said normal circuit closing position after circuit interruption to a circuit reclosing position, said closer when in normal circuit closing and reclosing positions having a first contact engaging said first terminal and a second contact engaging said second terminal, a dual characteristic fuse carried by said closer and electrically connecting said contacts when said closer is in its normal circuit closing position, and a switch member carried by said closer and normally in open circuit position when said closer is in normal circuit closing position and movable with said circuit closer to circuit closing position between said terminals when said closer is moved to said circuit reclosing position, said dual characteristic fuse comprisingtwo fusible sections in series relation when said closer is in its normal circuit closing position, one of said sections responsive to ambient temperatures of predetermined value produced by over-load currents in said one section and the other of said sections responsive to abnormal surge currents in said other 01 said sections in excess of a predetermined value.

2. A tubular bushing for a casing enclosing an electrical apparatus and a cooling medium, said bushing having an electric line terminal and an apparatus terminal, in combination with a circuit closer insertable in said bushing adjacent said line terminal and movable in said bushing from a first position to a second position, said closer including a contact engaging said line terminal and a contact engaging said apparatus terminal, a dual characteristic fuse carried by said closer and closing an electric circuit in said apparatus when said closer is in said first position, said fuse comprising two fuse sections normally in series with each other and with said contacts when said closer is in said first position, one of said sections responsive to ambient temperature of the cooling medium in excess of a predetermined value and the other of said sections responsive to surge currents in said circuit exceeding a predetermined value, and a switch member carried by said closer and normally in open circuit relation to said terminals when said closer is in said first position and movable with said closer into closed circuit relation to said terminals when said closer is moved to said second position upon rupture of said fuse responsive to either of said predetermined values.

3. In a circuit maker and breaker including a support having a pair of spaced terminals, a unit combination comprising a manually operable circuit closer mounted on said support and movable thereon from a first position relative to said terminals to a second position relative to said terminals, said closer including a fuse carried thereby and electrically connecting said terminals when said closer is in said first position and including also a conductor carried thereby and normally out of circuit closing relation to said terminals when said closer is in said first position and electrically connecting said terminals when said closer is in said second position.

v WILLXAM D. KYLE, JR.

Name Date Pittman Feb. 21, 1950 Number 

